IOUSDis must be written

src/toolsrc/ed.pla

@@ -994,8 +994,8 @@ def keyin3
 end
 def keyin2e
     byte key, vbl
-    ^$C07F // IOUDis: off
-    ^$C05B // Enable VBL Ints on a //c
+    ^$C07F = 0 // IOUDis: off
+    ^$C05B     // Enable VBL Ints on a //c
     repeat
         vbl = ^$C019
         if flags & showcurs
@@ -1008,8 +1008,8 @@ def keyin2e
         fin
         key = ^keyboard
     until key >= 128
-    ^$C05A // Disable VBL Ints on a //c
-    ^$C07E // IOUDis: on
+    ^$C05A     // Disable VBL Ints on a //c
+    ^$C07E = 0 // IOUDis: on
     ^keystrobe
     if ^pushbttn2 & 128 // Closed Apple pressed
         when key